To support various signal formats, current computers and audio/video apparati, for example DVD players, provide various data ports, for example USB (Universal Serial BUS) Port, VGA (Video Graphics Array) Port, HDMI (High-Definition Multimedia Interface) Port, DP (Display Port) Port, etc. The ports not only enable data transmission, but also supply power to some low-power-consumption devices, such as mobile phones, digital cameras, mouses, etc.
FIG. 1 shows an example in which a computer 10 supplies power to and transmits data to a mouse 11 via a USB port 12. As shown, the mouse 11 includes a voltage converter 13 and a microprocessor unit (MCU) 14. The USB cable encases four wires: a power supply wire 15, a ground wire 16, a positive data wire 17, and a negative data wire 18 (e.g., for differential data transmission). Wires 15 and 16 are coupled to the voltage converter 13 of the mouse 11 to obtain operating voltages for modules of the mouse 11, and the data wires 17 and 18 are coupled to the MCU 14 of the mouse 11 to enable data transmission between the mouse 11 and the computer 10.
In the configuration of FIG. 1, the port 12 not only enables the data transmission between the computer 10 and the mouse 11, but also enables power to be supplied from the computer 10 to the mouse 11. However, the power supplied via USB Port, DP Port, or HDMI Port is very limited because such power is mainly aimed at supporting data transmission. For example, a USB power wire typically provides a voltage of 5V, and the upper limit of current is generally about 950 mA. For another example, a DP Port typically provides a power of about 1.5 W. After it is coupled with a computer or an audio/video apparatus, the display device may fail to normally display the audio/video, operate unstably, or fail to operate in an optimum state if it operates by only using the power supplied via ports like a USB Port. Therefore, display devices usually also need to be coupled to another power source such as commercial power. However, this may lead to inconvenience during use. For example, positioning of the display device is restricted not only by data wires between the display device and the audio/video apparatus, but also by its own power-supply wire. In addition, there may be limited power sockets such that the audio/video apparatus and the display device cannot be used simultaneously.